The present invention relates to a technology for manufacturing a semiconductor laser and a technology for manufacturing a semiconductor laser module with the semiconductor laser built therein, and to, for example, a technology effective for application to a technology for manufacturing a semiconductor laser for optical communications.
In a wavelength division multiplexing (WDM) type optical transmission system, a demand for more speeding-up has been made even to transmission equipment with an increase in the amount (traffic) of data to be transmitted. A DFB (Distributed FeedBack) laser with a modulator for 10 Gbps DWDM (Dense Wavelength Division Multiplexing) built therein has been described in, for example, the November 2001 issue “Electronic Materials” by Institute for Industrial Research, P31-P33. A direct modulation DFB-LD (Laser Diode) or the like has been also described in the present reference.
Unexamined Patent Publication No. Hei 7(1995)-135369 has disclosed, as a semiconductor laser used as a light source for optical communications, a semiconductor laser wherein first and second electrodes are disposed on the same surface so as to allow flip-chip packaging, and a stray capacitance of a device is reduced to thereby enable handling of a high-speed operation. The same reference describes that a cutoff frequency f of a semiconductor laser (semiconductor laser device) becomes f=½πRC and a reduction in the capacitance C of the device allows high-speed modulation from this equation. The reference also describes that the capacity of a normal semiconductor laser in which two electrodes are opposed with a substrate and respective layers interposed therebetween, is one by adding a junction capacitance Cj formed between an active layer and a clad layer and a stray capacitance Cd developed between the electrodes.
The present reference has described that the semiconductor laser disclosed therein is formed on a semi-insulating substrate, and a minus electrode 12 and a plus electrode 20 are disposed so as to be electrically isolated from each other on the same surface, whereby the stray capacitance developed between the electrodes is greatly reduced.